In recent years there has been great interest in the captive breeding of chelonians (Frye, 1991) and in the possible manipulation of wild populations (Swingland and Klemens, 1989). Although reports of captive breeding of Kinixys spp. have appeared for example, K. homeana (Brown 1992) we have been unable to trace any previously published records of copulation, egg-laying and hatching of K. belliania in Africa. There is a paucity of information on the normal reproductive behaviour of most species in their natural environment or country of origin. In this paper we report observations on mating, egg-laying and hatching in a small group of Kinixys belliania kept at Morogoro, Tanzania.

The hinge-back (or hinged tortoise), Kinixys belliania, Bell's Hinged Tortoise, is found in many parts of Africa and, like other members of the genus, is distinguished by its hinged carapace (Garden, 1991) (Fig. 1.). The hinge appears to provide protection and it has been said to facilitate egg-laying. There is some disagreement about the taxonomy of the genus Kinixys (Pritchard, 1979; Swingland and Klemens, 1989; Broadley and Howell, 1991). The tortoises referred to in this paper were all considered to be K. belliania.

History

The detailed management of the tortoises will be described elsewhere (Cooper and Cooper, in preparation), as will the health of the animals and the various treatments given. The animals were kept on grass in a wired enclosure measuring approximately 4m by 4.5m in the grounds of Mafiga, a former colonial house, at Morogoro, 200km from Dar es Salaam, a locality in which the hinge-back is still found but is declining, probably because of habitat destruction. The diet supplied by grazing was supplemented by a selection of fruit, vegetables, cheese, egg and meat. The vegetation in the enclosure was similar to the wild habitat but with more grass and fewer dicotyledon plants.

The eleven original tortoises were acquired on 28 February 1992. They were rescued from a private collection where they could no longer be fed and cared for. Some were injured, having been attacked by a crocodile: limbs were missing and shells were damaged. One tortoise died soon after arrival, the other ten responded well to supportive treatment. The initial aim was to provide the group with a home and only gradually did it become apparent that they also had potential as a breeding herd.

Subsequently, two further animals needing assistance were added on 16 May 1992 and another, a small male, was donated to the group on 29 June 1993 at the end of the second nesting season.

All animals were considered to be adult and probably several years old. This report covers observations between March 1992 and September 1993.

Sex determination

At the time of arrival all animals received a full health check along the lines outlined in Beynon, Lawton and Cooper, (1992) but no specific attempt was made to sex them since the immediate need was to provide emergency accommodation and health care. Subsequently, following observation of copulation, animals were carefully examined and it was possible to see that the male hinge-back had a markedly longer tail than the female and a more concave plastron although the latter was not always easily distinguishable. The original group contained only one male.

Copulation

Reproductive behaviour was first noted in March 1992. No evidence of courtship behaviour in the form of shell butting was seen or heard at any time. The first evidence of mating was usually the finding of a male mounted on a female. Vocalisation was not a marked feature: respiratory grunts with the male's mouth open were sometimes noted but this was less marked and noisy than in the Leopard Tortoise (Testudo pardalis). There was no evidence that female tortoises with limb injuries had difficulty in mating or that copulation was more prolonged. It was not possible to assess the effect of injury on males since the only male in the group at that stage had no damaged limbs.

Egg-laying

Egg-laying by four tortoises was observed in 1992 during the last few days of May and, in the case of one tortoise, in mid-June; in 1993, eight or nine tortoises laid in mid-May and in the third week of June.

Egg-laying took place, usually after rain, late in the day and continued in the dark. A typical sequence of events was as follows: the female tortoise started digging shortly before dusk (although there were exceptions) and continued steadily until she finished; this could last 6-12 hours in tortoises with missing limbs but normal animals usually took up to 6 hours. The female dug with her hind legs alternately until there was a triangular hole pointing forward under her. The dimensions were those of the reach of her legs; towards the end of the digging she lowered herself a little into the hole to extend it further. She then stopped briefly and laid 1 to 4 eggs. This could be in quick succession or at intervals of up to 10 minutes. After an egg was laid she felt it with each hind leg in turn and pushed forward those that had preceded it. After the last egg was laid she started replacing the earth by pushing it from the pile of soil that she had put behind her during the excavation. At first she seemed to pick up only very small pieces of earth between her claws but later she scooped up larger amounts of earth with the whole leg. When finished, the soil had all been replaced by the female and the surface merely appeared rough. The area was fenced immediately after laying, in order to mark and protect the site and to enclose any hatchlings. The nest site was left undisturbed.

Although the hinge in the carapace was open when the eggs were laid there was no evidence that it played a significant part in the process.

Female tortoises with limb injuries generally took longer to lay eggs because of difficulty in digging and replacing soil. One animal with two healed stumps laid successfully in spite of this handicap (Fig. 2.). Injuries of the shell did not appear to affect the process except in one individual with serious carapace damage which was found to be egg-bound.

The adults received no dietary supplements before egg-laying but afterwards were given extra protein in the form of hard-boiled egg and ground eggshell as a source of calcium. Both these items were taken readily.

Hatching

The first young hatched in February 1993 following rain. They dug their way out of the earth and rested initially. In some cases their mud-covered shells were cleaned naturally by further rain but others were washed gently by hand. There was no sign of eggshells in any of the nests. Each hatchling measured between 4 and 5cm in length and weighed 15 to 22g One tortoise hatched with a developmental abnormality of the carapace on which some shields were divided to form two smaller ones. Data on egg weights, numbers and sizes of hatchlings and growth rates are to be published separately.

In the second laying season, May-June 1993, all the females laid and one egg was found on the surface of the ground without a nest. This and six other eggs of doubtful provenance were artificially incubated but failed to hatch. One tortoise laid twice (one egg, then two eggs) in the one season and at the end of June 1993 cloacae examination of all tortoises revealed that one female that had already laid still had at least one egg remaining in her oviduct. Cloacal examination was done wearing lubricated gloves and making a careful digital examination - a veterinary procedure as the cloacae wall can be perforated. Cloacal examination not only permits the cloaca itself to be investigated but also, through its wall, other structures such as bladder, kidneys and terminal gut.

Conclusions

In this short paper we have outlined our observations on the reproduction of a small captive herd of Kinixys belliana in Tanzania. We have intentionally concentrated on qualitative rather than quantitative aspects; a more detailed analysis of breeding records will be published elsewhere. Unlike captive breeding in Britain the eggs were left in situ to hatch as they were in the natural climatic range of the species. Observations showed how animals with leg injuries coped with egg-laying.

There is a need for more published data of reproductive behaviour of chelonians, especially in their country of origin and natural habitat as these may contribute to the success of captive breeding elsewhere. Sparse data can contribute substantially to the success of management programmes and to the conservation and welfare of the species. Although reports of captive breeding of Kinixys spp. have appeared, for example, K. homeana (Brown, 1992) we have been unable to trace any previously published records of copulation, egg-laying and hatching of K. belliana in Africa.

Acknowledgements

We are grateful to friends in Tanzania - the Lewis, Hook and Steel families and our staff at Mafiga, especially our gardener, Mohammed Ally - for their help in the care of the tortoises. Colleagues and veterinary students at Sokoine University of Agriculture assisted with the treatment of these animals.